A network analyzer measures the network parameters of electrical networks, such as s-parameters. A vector network analyzer measures both amplitude and phase properties, while a scalar network analyzer measures amplitude properties only. However, the precision of the measurements are typically impacted by the noises and errors introduced, for example, as a function of temperature and time, in the support circuitry, such as the test fixture, and the cabling of the network analyzers.
The electrical components in the signal path of fixture and the network analyzer may potentially produced phase, amplitude, and time delay distortions in the signal, and the generated distortion undesirably results in the signal being spread over a broader range of frequencies and time and impacts the accuracy of the measured parameters. As a result, calibrations need to be performed for the measurement “system” which includes both the network analyzer and test fixture to improve the accuracy and repeatability of the analyzer and the measured data.
Calibration of a multiport network analyzer entails measuring s-parameters of a set of specialized devices known as “calibration standards,” using the analyzer. A set of error coefficients for an error model of the measurement system is then calculated from the measured s-parameters using known values of the calibration standards. The error coefficients may be used to apply a correction to the “raw” s-parameters generated (measured) by the analyzer for the device under test (DUT). This technique essentially maps the measurement plane of the DUT to the Calibration plane of the network analyzer.
Furthermore, calibrating a multiple (N) channel RF test fixture for accurate s-parameter measurements of a RF DUT is substantially time consuming and cumbersome, since each port needs a calibration to be performed that is time consuming and complicated. Typically, each port requires a separate calibration procedure requiring at least 3 unique calibration standards (depending on calibration routine selected) to be loaded, measured, un-loaded, and stored for future retrieval for measurement reduction to completely and accurately characterize the test fixture.